Comments:EventID.Net
According to Microsoft a possible cause of this event`s appearance is The Internet Mail Connector (IMC), which omits one carriage return/line feed sequence (CRLF). For more information about this issue, see ME159286.

EventID.Net
As per Microsoft: "To avoid receiving the content conversion error stated above, install the proper code page for the character set referenced in the mail message". See ME163080 for more details.